Folding machine

ABSTRACT

An article folding machine, especially adapted to fold either a single or multiple lane input of plastic film bags, and capable of multiple folding modes by integral programming controls. Air jets force preselected fold line portions of the moving bags into nip rolls to successively fold each bag upon itself in preselected proportions and in two different directions. Selected folding operations can be bypassed.

United States Patent [191 Crawford et al.

[ 51 Feb. 5, 1974 FOLDING MACHINE [75] lnventors: Donald C. Crawford; Orrin 11-1.

Besserdich, Green Bay, both of Wis.

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: May 7, 1971 [21] Appl. No.: 141,127

[52] US. Cl 270/62, 270/66, 270/67, 270/69, 270/83, 270/86 [51] llnt. Cl B65h 45/12 [58] Field of Search. 270/81, 84, 61, 62, 69; 53/64, 53/77; 198/29, 38, 40

f 56] References Cited UNITED STATES PATENTS 3,252,700 5/1966 Henry 270/81 3,387,841 6/1968 Menell et al. 270/61 R 3,083,010 3/1963 Salmon et a1. 270/73 2,997,295 8/1961 Beck 270/62 2,766,045 10/1956 Morgan et al 270/61 R 3,578,311 5/1971 270/69 2,291,487 1/1942 Myers 270/81 Primary Examiner llarland S. Sltogquist Assistant ExaminerA. Heinz Attorney, Agent, or Firm-F. W. Anderson; C. E.

Tripp [5 7 ABSTRACT An article folding machine, especially adapted to fold either a single or multiple lane input of plastic film bags, and capable of multiple folding modes by integral programming controls. Air jets force preselected fold line portions of the moving bags into nip rolls to successively fold each bag upon itself in preselected proportions and in two different directions. Selected folding operations can be bypassed.

1 Claim, 28 Drawing Figures PATENTEDFEB sum swim near 13 FOLDING MACHINE BACKGROUND OF THE INVENTION The field of the present invention concerns apparatus for folding flat sheet-like articles, notably plastic film bags delivered at high production rates from a bag making machine.

DESCRIPTION OF THE PRIOR ART Specific prior art patents directed to folding devices for the most part concern the handling of laundry flatwork or textile goods, such as U.S. Pat. Nos. 3,252,700 and 3,437,334, and as contrasted to the production rates attained with modern bag making machinery, operate at rates so low as to make them unsuitable for other than their intended use. These and other folding devices are usually limited in one or more of the following respects: (1)The adaptability in handling various sizes of articles, (2) The capability of handling different numbers of input lanes, (3) The number, types and accuracy of sharply defined folds, (4) The folding of articles of different weight and flexibility, (5) Positive article control, (6) Ease of adjustment and maintenance, (7) The capability of selecting various drive ratios to provide the optimum velocities for the specific article being folded, and many others. Stated differently, prescut folding machines are relatively inflexible and are limited to a narrow range of folding installations.

SUMMARY OF THE INVENTION These various disadvantages of the prior art folding machines, and others, have been successfully overcome or minimized in the bag folding machine of the present invention by providing the following features:

1. Two folding elements are employed, a primary folder and a secondary folder wherein an article is first folded in one direction and then follows a different path to be folded in the opposite direction, and both folding elements operate with the articles in continuous motion.

2. The folding operation includes nip rolls to produce sharp creases along the fold line and the nip rolls from folding station to folding station have individual drive trains so that acceleration, deceleration or constant velocity for the articles can readily bechanged according to specific requirements.

3. Selected folding stations can be adjusted to bypass the normal folding operation without altering the normal conveying path of the article.

4. The various elements which manipulate and convey the articles are governed by a built in control system which is easily programmed to effect different numbers and types of folds.

5. Either single or double lane input can be accommodated without structural changes, and the following machine is readily adaptable to handle a three lane input, or more,

6. A modular construction provides, with only minor structural modifications, for use of the primary folder without the secondary folder for installations requiring only a single-direction folding operation.

7. Numerous unique refinements and modifications of the known folding concept result in exceptional folding accuracy at high production rates, i.e., folds within about i three-sixteenths of an inch at an article input velocity of up to 600 feet per minute.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the article folding machine of the present invention.

FIG. 2 is a longitudinal section. through the article folding machine.

FIG. 3 is an end elevation indicated by lines 3-3 on FIG. 2.

FIG. 3A is an enlarged fragmentary elevation of a nip control mechanism shown in FIG. 3.

FIGS. 4 and 5 are enlarged sections of an article folding station shown in FIG. 2, and respectively illustrate the successive stages of the initial part of a folding operation.

FIG. 6 is a section taken along lines 6-6 on FIG. 4.

.FIG. 7 is an enlarged isometric view of a nip control mechanism indicated by the arrow 7 on FIG. 6.

FIG. 8 is a section taken along lines 88 on FIG. 4.

FIG. 9 is an enlarged section of part of the apparatus shown in FIG. 3, and is taken along lines 9-9 on FIG. 2.

FIG. 10 is an enlarged section taken along lines 10-10 on FIG. 1.

FIG. 11 is a section similar to the central portion of FIG. 9.

.FIG. 12 is a section similar to FIG. 11, but showing a different operational position.

FIG. 13 is a section taken along lines 13-43 on FIG. I 1.

FIG. 14 is an isometric of the overall drive train.

FIG. 15 is a schematic plan illustrating a single lane input, four fold operation.

FIG. 16 is a schematic plan illustrating a double lane input, four fold operation.

FIG. 17 is a schematic plan illustrating a double lane input, three fold operation.

FIG. 18 is a schematic plan illustrating a single lane input, three fold operation. I

FIGS. 19-22 are schematic plans of a second embodiment of the invention and respectively illustrate (1) a single lane, double fold operation, (2) a double lane, double fold operation, (3) a single lane, single fold operation and (4) a single lane, double fold operation where the article is reduced to one-third size.

FIG. 23 is a fragmentary elevation of a second embodiment of the invention where the primary folder is used alone and produces the folding operations shown in FIGS. 19-22.

FIG. 24 is a section of the structure underlying the apparatus shown in FIG. 23.

FIG. 25 is a schematic plan showing the location of various scanning and folding elements.

FIG. 26 is a schematic diagram illustrating one form of program control for the FIG. 25 scanning and folding elements.

FIG. 27 is a programming chart showing the setup procedure for producing the folds shown in FIGS. 15-22.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In brief outline, the article folding machine 30 (FIG. 1) comprises a primary folder PF and a secondary folder SF which extends perpendicular to the primary folder. A number of later identified and described conveying surfaces transport flat articles through the folding machine 30 from the inlet end 36 to the discharge end 38, and are all formed of a series of round endless elastic belts. The articles, such as plastic film bags B, pass under a plurality of retro-reflective photoelectric scanners S1S8 for triggering the various folding operations.

Two sets of folding elements are provided in the primary folder PF, a first set of folding elements at a folding station PF 1, and a second set of folding elements at a folding station PF2. Four sets of folding elements are provided in the secondary folder SF, but only two or three sets of elements are active at the same time.

One or more of the folding stations SF 1, SF2 and SF3 perform the first folding operation in the secondary folder SF, and the folding station SF4 performs the second folding operation. Thus, when a single lane of bags is being processed, a set of folding elements at a folding station SF2 and a set of folding elements at a folding station SF4 are active. If a double lane of bags is being processed, a set of folding elements at a folding station SP1 and a set of folding elements at a folding station SF3 are used in conjunction with the folding station SF4. In both cases, only a single lane output is employed, and up to four folds can be made on any one bag inthe entire folding machine. In each case, a folding operation is initiated when an air tube Al, A2, A3, A4, A5 or A6 is actuated by one or more of the scanners 81-58 to direct an air blast against the bag and tuck that portion of the bag into nip rolls.

As will later be described, certain folding operations can be bypassed without deflecting the bag from its normal conveying path. Provision is also made for redirecting incoming bags out of the folding machine if the incoming bags are temporarily not up to production standards and should be rejected. The primary folder PF is also usable alone for those installations which do not require more than the single direction, double transverse folds produced inthe primary folder PF.

The primary folder PF handles a double lane of bags on input lanes A and C, and a single lane of bags along an input lane B. In the first case, the scanners S1, S2, S3 and S4 are active when two folds are produced in the primary folder PF. If only one fold is required, one of the other pairs of scanners S1, S2 and S3, S4 may be made inactive. With a single lane input, the scanners S1 and S3 are active on lane B, and the scanners S2 and S4 are made inactive. For the secondary folder SF with single lane input, the sensor S6 of the secondary folder SF is active, while a double lane input is handled by sensors S7 and S5. With either a single or double lane input, the bags are moved along the secondary folder SF sidewise in a single lane relative to their former direction of movement, under the scanner S8, and are discharged at the discharge end 38 for packaging by other apparatus, not shown.

It should be noted here that the later disclosed arrangement of folding stations and controls for programming the operation of these stations is merely by way of example, and that the article folding machine 30 can be provided with different control combinations and folding stations according to the same inventive concept, as may be required for specific installations where different numbers of input lanes and different numbers or types of folding operations are needed. Various structural features and arrangements provide this flexibility of the article folding machine 30 to accommodate different requirements, and comprise important features of the present invention, as will be evident from the following detailed description.

PRIMARY FOLDER It is assumed that the folding machine 30 (FIG. 1) is programmed, by a later described control circuit, to handle a single lane input of articles such as plastic film bags B, one of which is shown in phantom outline at the inlet end of the machine. The primary folder PF includes spaced frame plates 40 and 42, and the secondary folder SF includes frame plates 44 and 46 which are cantilevered toward the discharge end 38, as shown in FIG. 3. The latter frame plates are supported by apertured brackets 48, which form extensions of the primary folder frame plates 44 and 46.

An inlet conveyor 50 feeds incoming bags B directly from a bag making machine, not shown, or from any suitable intermediate conveyor into the folding machine 30. The bags are preferably fed with a closed end in leading position, such as with the side seam of a sideweld bag extending across the conveyor 50. The bags move continuously through the primary folder PF (as well as through the secondary folder SF) and are fed one by one to the first folding station PFl, best shown in FIGS. 4 and 5.

With reference to FIGS. 2 and 4, the inlet conveyor comprises a grooved idler roller 52, a plurality of round elastic endless belts 54 extending across the roller 52, and a grooved, driven turning roller 56. In order to grip the bags, the upper flight of the inlet conveyor 50 cooperates with the lower flight of a hold-down or gripper conveyor 58, the belts 60 of which lie between the belts of the inlet conveyor and are trained around a driven roller 62 and an idler roller 64. A guide roller 66, adjustably mounted to each sidewall 40 and 42 by a bracket assembly 67 that provides both elevational and fore and aft adjustment, depresses the lower flight of the gripper conveyor so as to form an entrance throat for the bags with the subposed inlet conveyor flight. In the usual manner, the gripper and inlet conveyors operate at the same linear velocity and slightly faster than the velocity at which the bags are delivered into the folding machine 30 so that the bags and any wrinkles therein tend to be drawn taut.

The leading edges of incoming bags are directed over the turning roller 56 to the first folding station PF 1 by round elastic turning belts 68 that are trained around the gripper conveyor roller 62 and a grooved upper nip roll 70. One flight of the belts 68 engages a segment of the turning roller 56, and due to the elasticity of the belts 68, the bag is tightly gripped against the turning roller. As the leading edge portion of a bag descends out of contact which the belts 54 and 68, it is supported by an inclined flight of round elastic belts 71 that are trained in grooved portions of the turning roller 56 and in corresponding grooves in an idler roller 72.

Meanwhile, the trailing end of the bag is approaching the scanners S1 and S2 (FIG. 1), and when a predetermined transverse fold area of the bag is opposite the nip between the upper nip roll and a cooperating lower nip roll 74, as shown in FIG. 4, a light beam from the scanner S1 (scanner S2 is inactive with a single lane input) is reflected from a reflective tape 76 mounted on the upper surface of a reflector mounting bar 78 as the trailing edge of the bag passes beyond the light beam. The reflected light is sensed by the scanner, and an amplifier and scanner pulse control circuit in a control cabinet 80 utilize this signal to energize pilot valve operated, solenoid controlled air valves for apredetermined time duration. In the present case where the folding machine 30 is handling a single lane input of bags, air valves V1 and V2 (FIG. I) are simultaneously energized by the scanner S1 and air under pressure is transmitted from an air reservoir R1 through flexible air tubes 82 (FIG. 4) to a rigid, perforate air tube Al. The air reservoir R1 is individual to the air valves Vll and V2 and is supplied with pressure-regulated air. The reservoir also provides a tie bar connection to the main frame plates 40 and 42.

As best shown in FIG. 6, pilot airfor the air valves VI and V2 is supplied by pilot air inlet tubes 83 from a separate source (not shown) of pressure regulated air. In order to provide rapid opening of theair valves, the pilot air is supplied at a pressure above normal requirements for operating the valves at about 55 psi. This pneumatic over-excitation, together with electrical over-excitation of the solenoid of the valve, and in combination with the specific design employed for the air tube All, yields extremely fast response for the air tucking operation. I

The electrical excitation is by means of capacitordischarge energization so that the initial voltage is several times the rated holding voltage, for example, 33 volts for a 6 VDC solenoid, thereafter dropping to about the holding voltage as the capacitor is discharged. The net result is that no damaging heating of the solenoid coil occurs, yet in about 2milliseconds the valve is fully opened and air pressure is uniformly distributed within the air tube Al. The tucking air is then delivered for about 30 milliseconds. In addition to this rapid response, the described electro-pneumatic system offers a high degree of repeatability. This makes possible the use of relatively high bag conveying speeds and relatively small spacing between incoming bags, and it will be evident that these factors in turn contribute to the attainment of accurate folding at high production speeds.

Air tube Al is provided with a series of small apertures (one thirty-seconds of an inch diameter on onehalf inch centers in a tube about nine-sixteenths inch ID) aligned along the tube and radially directed, as shown by the air flow arrows in FIGS. 4 and 5, toward the nip of the nip rolls 70 and 74h Thus, the fold line portion at $4 (FIG. 5) aligned with the air tube apertures is buckled outward away from the support belts 71 when the air valves are energized, and into the nip rolls of the first folding station PF 1. It will be noted that the trailing portion of the bag is gripped between the inlet conveyor belts 54 and the gripper belts 60, and between the turning belts 68 and the turning roller 56, so that the bag remains under positive control while the buckled portion is drawn up and formed from the depending portion of the bag contacting the support belts 71.

In order to locate the fold line of the bag, the scanner S1 is adjustable along the conveying path of a mounting bar 81. The bar 81 is supported by an overhead rod 83 that is connected at a selected point along an angle bar 85 mounted on the main frame plate 40, and includes a T-shaped slot 87 which receives a collar 89 fixed to the upper end of a threaded stud 911. A wing nut 93 locks the stud in a selected position along the slot 87 and the stud is gripped by a clamp 95of the scanner for vertical positioning and for swinging adjusting movement of the scannerabout the axis of the stud 91. Provision is also madefor adjusting the air tube Al (FIG. 6) rotationally about the axis of end brackets 97, and toward, and away from the tucking nipv by slotted mounting bars 99 which clamp the air tube as shown in FIGS. 4 and 5 so that the air tube can be rotatively adjusted about its own axis. The scanner is electrically coupled to an adjustable time delay circuit located in the control cabinet so that the length of the bag does not limit varying the location of the fold line.

Thus, very short bags which do not reach from the scanner to the turning roller 56 will trigger the scanner, and by means of the time delay circuit will cause the air valve to be actuated when the appropriate area of the bag is subsequently aligned with the nip rollers. With a very long bag which extends from the scanner to a point beyond the nip rollers, 21 minimum time delay and/or repositioning the scanner enables a folding operation along any selected transverse fold line trailing portion. All of the previously identified scanners are similarly mounted for fore and aft adjustment, and are each associated with an adjustable time delay cir' cuit.

The once folded bag B conveyed through the nip rollers "l0 and 74, as shown in FIG. 5, passes over a series of wire bridge members 96 that are clamped to transverse angle bars 98 and MM). It will be noted that each bridge member 96 (FIG. '6) extends around the lower nip roll 74 in a groove of the roller, and lies below the surface of the roll so that the nip rolls maintain maximum driving engagement with the bag as it enters a transfer conveyor llll.

With reference to FIG. 6, several important details of the air tube All, the nip rollers 70 and '74, and the conveying belts should be noted. The air tube All is internally blocked at its center I03, and the air valves V1 and V2 have individual yoke connections to the two halves of the air tube to minimize the response time for pressurizing the entire tube. In conjunction with the proximity of the air reservoir RI and the short connections to the air tube All, the previously noted rapid response to the triggering action of the scanners for the air tucking operation is attained. Conventional hose fittings to the valves were found to be too highly restrictive for satisfactory air flow, but a simple alternative is a tubing fitting with male threads and a short length of tubing soldered therein for a clamped connection to the flexible air hoses 82.

The round section elastic belts 711, and the others used throughout the folding machine, permit the close one-half inch aperture spacing along the air tube Al without masking any of the apertures. Thus, the air tube apertures are numerous and small, and because of this, can provide a relatively uniform pressure build up and distribution after build up for the period when the air jets are accomplishing the tucking. This high degree of pressure control results in air conservation and permits rapid sequencing of successive folding operations so as to achieve high production rates.

A feature of considerable importance is that each bag is manipulated in such a way as it passes over the turning roller 56, that the leading end of the bag tends to be deflected away from the nip rollers and to follow the support belts 71. This result is accomplished by providing a slightly faster linear velocity for the elastic turning belts 68 than the peripheral velocity of the turning roller 56. In this way, the uppermost wall of the bag is advanced slightly beyond the lowermost wall of the bag. Because the leading edge of the bag is closed (or sealed, in the case of a sideweld bag) the differential movement of the two walls urges the leading edge of the bag toward the support belts 71 and away from the nip rolls. This feature is considered to be especially important when handling lightweight bags that are particularly vulnerable to windage, and is very effective in preventing premature entry of the bags into the nip rolls.

As best shown in FIGS. 4 and 5, the wire bridge members 96 are each provided with a linear lower leg 107 which, together with an adjacent segment of the arcuate portion extending around the lower nip roll 74 lies outwardly away from its associated groove in the nip roll. This assures that the bag will not prematurely enter the nip rolls, and that the nip rolls can be surfaced, as in the present case, with a resilient sleeve affording high frictional engagement with the bags.

Conveyor 101 (FIGS. 2, 4 and includes a lower set of driven endless belts 102, trained around a driven turning roller 104 and an idler roller 106, and an upper set of driven endless gripper belts 110, trained around an idler roller 112 and a driven roller 114. An adjustable idler roller 115 contacts the lower flight of the belts 110. Rollers 104 and 114 are similar to the previously mentioned rollers 56 and 62, and perform a simi lar function. Thus, an upper nip roll 116 for the second folding station PF2 is mounted adjacent the turning roller 104, and a series of elastic turning belts 118 are trained around the nip roll 116 and the roller'l14, with one flight wrapped over a segment of the turning roller to tightly grip the folded bags.

Because the length of the bag is now a fractional part of its former length, the scanner S3 is mounted close to the turning roller 104 so that the light beam directed onto and returned from a reflective surface on a reflector mounting bar 120 triggers the air valves V3 and V4 when the next fold line of the bag is opposite an air tube A2. Meanwhile, the free, depending leading end portion of the bag is supported by a series of belt flights 130 that are trained around the turning roller 104 and an idler roller 132.

In the same manner described for the folding station PF], the bag portion impinged by the air jets from the air tube A2 when the valves V3 and V4 are triggered is blown or tucked into the nip between the upper nip roll 116 and a lower nip roll 134. In the same manner described for the first folding operation in connection with FIGS.-4 and 5, the nip rolls of the folding station PF2 advance the bag over a series of wire bridge members 136 that are clamped to angle bars 138 and 140, and extend around the lower nip roll 134. The bridge members support the bag as it is fed by the cooperating upper and lower nip rolls onto a series of belts 142 of a delivery conveyor 144.

Supported by a driven roller 148, and an idler roller 150, the belts 142 are cooperatively associated with a series of gripper belts 152 carried by an idler roller 154 and a driven roller 156, and have lower flights guided to form an entrance throat for the bags by an adjustable idler roller 158. A series of wire bridge members 159 similar to the bridge members 134, extend around the driven roller 148 and an adjacent later mentioned roller 204 to support the bags ejected from the primary folder.

PRIMARY FOLDER DRIVE In accordance with another feature of the present invention, the primary folder PF is provided with individual drive trains for the first folding station PF 1, the second folding station PF2, and the delivery conveyor 144 so that the conveying velocity of the bags through the machine can be initially made optimum for the specific weight, type, size, etc. of bag being processed, and so that the bags can be progressively decelerated, if desired, with accurate velocity changes to attain the best folding accuracy and control of the folded bags discharged from the primary folder PF onto the secondary folder SF. For these purposes, all of the drive components are powered by a single variable speed motor drive unit M (FIG. 2) having a cog belt drive connection 160 to a jackshaft 162.

A cog belt and pulley drive connection 164 transmits power from the jackshaft 162 to the turning roller 56 of the first folding station PFl, and a similar drive train 166 on the same jackshaft powers the turning roller 104 of the second folding station PF2. Each turning roller 56 and 104, by means of later mentioned gearing, powers its associated nip rollers. For driving the delivery conveyor 144, a second jackshaft 168 is driven from the jackshaft 162 by a cog belt and pulley arrangement 170, and a cog belt 172 transfers power to the delivery conveyor roller 148. The primary drive pulleys of the drive trains to the folding stations PF 1, PF2 and the delivery conveyor 144 are readily accessible on the jackshaft 162 and 168 to alter the conveying velocity of the bags through the primary folder as suits the particular handling requirements of a specific type of bag.

According to another feature of the present invention, the primary folder PF can be used as a separate machine without the secondary folder SF, or the functions of the primary folder can be used without the functions of the secondary folder when the two folder sections are incorporated into one machine, or the combined functions of the primary and secondary folder can be used. In the first instance, the bags can be directly discharged from the delivery conveyor 144 of the primary folder PF when the bags are made of relatively inflexible material. When relatively flexible bags are being handled, it is usually necessary to add a conventional corrugator roll assembly, later shown and described, at the discharge end of the delivery conveyor 144 in order to provide temporary corrugations lending beam strength to the bags so that they do not collapse during discharge.

NIP ROLL MOUNTING A particular and important feature of the invention is that the lower nip rolls 74 (FIGS. 4 and 5) and 134 (FIG. 2) are resiliently biased at each end to a preselected operating position by similar mechanisms, as shown in FIG. 7 for one end of the nip roll 74. This mechanism includes a nip roll bearing 173 mounted in a sliding block 174 which is slidably engaged with guideways 175 that are pinned to the frame plate 42. A collar 176 on the upper end of an axially positionable adjustment bolt 177 is retained in a recessed portion of the block 174 which is closed by a plate 179. Limited movement of the sliding block 174 relative to the collar 176 is provided for, and a compression spring 181 is mounted on the bolt 177 between the plate 179 and an adjusting nut 183.,By positioning the adjustment bolt 177, operating clearance between the upper and lower nip rolls is established, and the lower nip roll can be downwardly deflected from this position for about oneeighth of an inch so as to allow for entrapped air or thickness variations in bags gripped between the nip rolls.

Mos improtant is that the spring biased nip roll mounting affords a procedure for selectively bypassing the folding function of either folding station PF1 or PFZ for a production run without deflecting the bag from its normal conveying path. For this purpose, a spacer 185 is inserted under the collar 176 so that the lower nip roll '74 is moved downwardly away from the upper nip roll the thickness of the collar (about onesixteenth of an inch) in addition to the normal operating clearance between the upper and lower nip rolls.

Thus spaced apart, there is an air passage between the nip rolls to allow air from the air tube Al (or A2) to pass between the nip rolls without creating air turbulence in the path of the bag. The air pressure is preferably also reduced in the air reservoir R1 toinhibit turbulence.

The air valves V1 and V2 (FIG. 6) as well as the air valves V3 and V4 previously mentioned are each provided with a locking manual actuator button at 187. When depressed, the button holds the valve open so that air is continuously supplied to the air tube 82. Thus, as is easily understood from FIG. 4, when the leading edge of a bag first enters the air jets from the air tube, that edge is forced between the nip rolls 70 and 74 by the continuous air blast so that the normal folding operation does not occur, yet the bag proceeds along the same conveying path used in the normal folding mode. In the case of the folding station SF4 of the secondary folder SF, the second folding operation can be bypassed by one of several means, later described.

The secondary folder SF (FIGS. 9 and 10)includes pairs of nip rolls 188, 189, 190 and 191, the down stream roll of each pair being resiliently mounted in a manner similar to the mounting of the primary folder nip rolls 74 and 134. FIG. 3A illustrates the mounting for the downstream roll of the pair of rolls 189, and is typical of the mounting for the downstream roll of the nip roll pairs 188, 190. The mounting for the last pair of rolls 191 is shown at 192, FIG. 3, and is similar, but inverted. In each case, the upstream nip roll is fixed in position.

The mounting shaft 193 (FIG. 3A) of the downstream nip roll 189 projects through a clearance aperture in the frame plate 46 and is rotatably mounted in a pivot bracket 194 pivoted at 195 to the frame plate. A compression spring 196 biases the lower end of the pivot bracket against an axially adjustable stop bolt 197, the adjusted position of which regulates the clearance between the fixed nip roll and the movable nip roll of the pair of rolls 189 so that the nip clearance of the rolls can be preset to the thickness of the bag, while the resilient mounting will accommodate variations in thickness and any entrapped air in the bags. An axially adjustable spring holder 198 allows adjustment of the spring pre-load.

SECONDARY FOLDER Returning to the present instance in which the secondary folder SF and all of its folding functions are employed, the bags are discharged from the delivery conveyor 144 of the primary folder PlF onto an input conveyor 206 (FIGS. 2 and 3) of the secondary folder SF. The input conveyor 200 comprises a series of endless belts 202 trained around grooved idler and drive rollers 2114 and 2116., respectively, and carries the bag past the scanners S5, S6 and S7, and against three fixed bag stops 2117. ln the present single lane operating mode, only the folding station SP2 is actuated. The nip between the pair of nip rolls 189 at the folding station SP2 is aligned with LANE B so that the: bag is centered over the nip rolls. The nips between the pairs of nip rolls 188 and 191) are in similar manner aligned with LANE C and LANE A at the folding stations SF1 and SF3.

After the bag comes to rest against the stops 297, the solenoid operated air valve V6 is energized. Thus, the scanner S6, previously actuated as it sensed the trailing edge of the bag, energized its associated time delay circuit in the control cabinet and the time delay period allowed the bag to become squared up relative to the stops if it was delivered slightly askew, and to thus be properly positioned before the air valve V6 transmits air under pressure from an air reservoir R3 to the air tube A4. However, it is probable that the twice folded bag B now has a radiused leading edge because most plastic film materials will not long :retain a sharp crease.

Accordingly, for some heavier web materials it may be necessary to flatten and pre-crease the bag along the subsequent fold line so that the air jets from the air tube A4 can force the entire fold line area of the bag into the pair of nip rolls 189. For this purpose, the pilot air pressure which is internally switched on to actuate the main plunger of the valve when the valve solenoid is actuated, is also used to power a breaking or creasing unit 2118, best shown in FIGS. 9 and 1 1-13, which depresses the leading edge portion of the bag B before the air jets impinge the bag.

The working edge of the creasing unit is a rod 210 which has an upwardly curved upstream end to guide the bag under the rod, and is secured to an angle bracket 212. The angle bracket is fastened to the piston rod of a small fixed air cylinder 214. An air, supply tube 216 delivers part of the pilot air from the air valve V6 to the air cylinder 214. Therefore, because there is some small time delay period before the pilot air opens the valve V6, the pilot air causes the creasing unit 168 to thrust the rod 2111 downwardly against the bag as shown in FIG. 12, and both crease and flatten the edge of the bag along its subsequent folding line at or before the time the air jets from the air tube A4 strike the bag. Thus pre-creased, the air jets from the air tube A4 then force the fold line portion of the bag past fixed nip guards 218 and into the pair of nip rolls 159, and the bag, now folded along a line normal to its two previous folds, is discharged onto a takeaway conveyor 220 (FIG. 3) for delivery to the second folding station SP4 of the secondary folder SF.

Because smaller bags are usually formed of relatively more flexible material, when the article folding machine is used with a two lane input, the air tube A3 of the folding station SF1, and the air tube A5 of the fold-. ing station SP3 do not ordinarily require a creasing unit to pre-crease the bags. If unusually inflexible bags are being handled, a creasing unit can be employed with each air tube A3 and A5, and operated from the associated air valves V7 and V5, respectively, in the same way described in connection with the air valve V6.

The takeaway conveyor 220 (FIG. 3) comprises a series of spaced endless belts 226, trained around the fixed, driven one of the pair of nip rolls 191 (FIGS. 1 and and around an idler roller 230. The spring biased, downstream nip roll is mounted beneath a dead plate 234 that is lower than the fixed nip roll. Thus, if the last folding operation is required, the leading edge of the bag passes over the dead plate 234 onto a belt conveyor 236. Meanwhile, the scanner S8 senses the trailing edge of the bag and the valve V8 is triggered to provide air from an air reservoir R4 to the air tube A6 when the center of the bag is aligned with the nip between the pair of nip rolls 191. Subsequent to this folding operation, the bag, now folded four times, is deposited upon a discharge conveyor 240 and ejected from the folding machine 30 to other handling means associated therewith. If the fourth folding operation is not required, later described provisions allow the fold to be bypassed.

As in the case of all the conveying surfaces in the machine, the conveyors 236 and 240 are formed of spaced elastic belts 242 and 244, respectively. The former belts are trained around a grooved idler roller 245 and a grooved drive roller 246, and the conveyor 240 includes grooved idler and drive rollers 247 and 248.

SECONDARY FOLDER DRIVE Best shown in FIG. 14, the drive train for the secondary folder SF includes a cog belt and a pulley connection 250 from the jackshaft 168 to a shaft 252 that drives right-angle gear boxes 254 and 256. All of the pairs of nip rolls 188, 189, 190, 191 (FIG. 14) are simultaneously rotated at the same angular velocity. For this purpose, the gear box 254 powers three shafts 260 which are interconnected by chain drives 262, and

which each carry an individual chain drive 264 to the fixed, upstream roll of the pairs of nip rolls 188, 189

and 190. Each of the resiliently mounted rolls at folding stations SFl, SP2 and SP3 is driven from its associated fixed nip roll via intermeshed gears at 266. In similar manner, the nip rolls at the folding station SF4 counterrotate by means of gears 167, and each setof the nip rolls of the primary folder PF are counterrotated by three intermeshed gears at 268, one of which is mounted on each of the driven turning rollers 56 and 104.

The right angle gear box 256 drives the fixed nip roll of the folding station SP4 via a shaft 270 having a chain drive connection 272 to the nip roller, a similar drive train 274 to the conveyor drive roller 246, and a third drive connection 276 to the conveyor drive roller 248. The shaft 252 which powers the gear boxes 254 and 256 also powers the conveyor drive roller 206 by a cog belt and pulley connection 278.

As previously indicated, one of the important features of the conveying and drive system is the ease with which the primary folding stations drive ratios can be individually changed to suit particular requirements. Thus, the cog belt and pulley drives 164 and 172 are situated outside the frame plate 42 (FIG. 1) in a guard housing 280 (FIG. 2) for accessibility. Similarly, the cog belt drive connections 250 and 278 (FIG. 14) are readily accessible for the same purpose, whereby different ratio drives can be installed to vary the folding speeds of the secondary folder and the conveying speeds of incoming and outgoing bags for the secondary folder.

EXEMPLARY FOLDING MODES FIGS. 15-22 schematically illustrate only a few of the possible folding combinations and operating modes of the folding machine 30, but serve to indicate the numerous possible combinations that can be used. In FIGS. 15-18 both the primary and secondary folders PF and SF are used, while in FIGS. 19-22 the primary folder PF is used without the secondary folder SF. In each Figure, the edge profiles of the bags are shown outside the folding machine opposite the plans of the bags being folded within the folding machine.

FIG. 15 shows a single lane input, four fold operation wherein each bag is folded in half at each successive folding station PFl, PF2, SF2 and SF4. In this folding mode, only the scanners S1, S3, S6 and S8 are active, and the scanners S2, S4, S5 and S7 are electrically disabled. Both halves of each air tube Al and A2 are operated by the scanners S1 and S3. The structural provisions and programming method to accomplish the FIG. 15 folds, as well as the FIG. 16-22 folds, are later described.

FIG. 16 shows a double lane input, four fold operation, with all folding stations operative. The important aspect of this mode of operation is that the scanners S1 and S3 are manually repositioned relative to their respective mounting means so as to cover LANE A, all scanners except S6 are active, and the halves of each air tube A1 and A2 are separately energized. As shown in FIG. 6, an extra reflective tape and its support means may be permanently mounted in LANE A at folding station PF2 for the repositioned scanner. Similar provisions are made at folding station PFl.

FIG. 17 illustrates a double lane input similar to FIG. 16 except that only three folds are made and the last fold is bypassed at folding station SF4. The two sections of each air tube Al and A2 are separately energized.

FIG. 18 shows a three fold operation with a single lane input, scanners S2, S4, S5, and S7 being inoperative, and the fold at folding station SF4 being bypassed. Both halves of each air tube A1 and A2 are simultaneously energized.

An important point to note relative to FIGS. 15-18 is that for a single lane input, the centrally located scanners S1, S3 and S6 of LANE B are used, and that for a double lane input the scanners S1 and S3 are relocated to cover LANE A and operate in conjunction with the scanners S5 and S7 that are aligned with and corresponding to LANE A. Because the scanners S1 and S3 are so easiliy accessible and movable, (as are all of the scanners) it is believed an unwarranted cost to provide permanent scanners for both LANES A and B of the primary folder PF.

Due to the modular construction of the primary and secondary folders PF and SF, the primary folder is easily separated from the secondary folder and is usable alone in installations requiring only two, in-line folding operations. In this regard, it may be noted that the incoming bags may have already been pre-folded to some extent during their manufacture, and that either embodiment of the invention the folding machine comprising only the primary folder PF, or the machine comprising both folders PF and SF can handle an input of pre-folded bags. Further,-it can readily be seen that a three lane input can be provided if the bags are small enough, or if the machine is widened for larger bags, and that additional folding stations can be added 

1. In a sheet folding apparatus of the type including a primary folder having conveyors for transporting a sheet to folding stations, said folding stations including folding rolls operable to fold the sheet to a fraction of its original dimensions, a secondary folder having a folding station including folding rolls for performing additional folds on said folded sheet, said secondary folding station including conduits for emitting jets of air to the nip of said folding rolls; the improvement in said secondary folder comprising means for precreasing and urging said sheet toward the nip of said secondary folding rolls, said precreasing means comprising a thin, reciprocable creasing shoe overlying and engageable with said sheet when said sheet is located over said pair Of folding rolls, means for moving said creasing shoe into engagement with said sheet along a line parallel to the nip defined by said pair of folding rolls which line is generally normal to a previous fold line, control means responsive to the presence of a sheet at said pair of folding rolls for bringing said creasing shoe in contact with said sheet to partially direct said sheet into the nip of said rolls, and means for substantially simultaneously connecting said conduit with a source of air under pressure to completely direct said sheet into the nip of said rolls. 